Using your criteria, of course.

Personally, I prefer Root Beer to Coke. It would never ocur to me to write a post about how silly it is for people to drink coke when they could be drinking Root Beer.

But since you brought it up, battery life is a major reason I prefer my 510 to my iPhone for a bike computer. While I see your point, I don't always start a ride with my phone at 100%. There isn't always a charge available at the end of a ride. Sometimes I stop for lunch and want to use my phone to email/facebook/makecalls/generally burn battery life. I like to use my phone for a camera. Etc, etc., etc.

Also, if my Garmin runs out of power mid ride, I'm annoyed, but I'm not in danger or seriously inconvenienced. If my phone goes out on me mid ride, I could conceivably be stranded or worse.

So I prefer the 510.

FWIW, it also has more configurable screens for monitoring data, uploads directly to Garmin/Strava/Training Peaks/RWGPR/MMR, is rain proof, is less attractive to theives, and costs roughly 1/2 of what my last replacement phone cost. It's apso covered by Garmin's post-waranty replacement policy - I can replace it for around $80 if I mess it up (My last one got run over after it fell off during a race - $80 and a few days and I had a reconditioned 510).

Put me in the Bike computer beats iPhone by a mile category.